1. Field of the Invention
This invention relates to a motor case, and more particularly to a motor case whose outer size is reduced as much as possible.
2. Description of the Related Art
As one example of techniques of reducing the outer size of a motor (such as a stepping motor) as much as possible, there is known a construction in which notches are formed respectively in side wall portions of a motor case to provide openings, and the outer peripheral surfaces of coils of a stator are exposed to these openings (JP-A-2002-238199).
Usually, an air gap is formed between an outer peripheral surface of a coil and an inner surface of a motor case so that the coil will not contact the motor case, and therefore the width or outer size of the motor case is equal to the sum of the coil diameter, the air gap and the wall thickness of the motor case.
On the other hand, in the motor of JP-A-2002-238199, the distance between the parallel side wall portions (flat surface portions) of the motor case of a generally oval shape (as seen from the front side thereof) is equal to or slightly smaller than the diameter of the coil, and also the side wall portions are notched to provide the openings, and the outer peripheral surface of the stator coil is exposed to these openings. With this construction, the motor width is reduced into a dimension generally equal to the coil diameter.
In the motor disclosed in JP-A-2002-238199, the parallel side wall portions of the motor case are notches to provide the openings, and the outer peripheral surface of the stator coil is exposed to these openings, and with this construction the motor width is reduced. However, the coil is exposed to the openings in the motor case, and therefore a space must be provide around the motor so that a frame, a chassis or other electronic parts of an electronic equipment will not contact the coil, and this invites a problem that an advantage, achieved by this compact design, is reduced.
Therefore, there arises the technical problem to be solved in order to reduce the size of the motor case as much as possible and also to achieve the high-density mounting of the parts while eliminating a fear that the coil contacts the frame and electronic parts.